Not applicable.
1. Field of the Invention
The present invention relates generally to trailer hitches, and more particularly to an improved anti-sway trailer hitch.
2. Discussion of Related Art
The vast majority of passenger vehicles include rear substantial area of mass which projects rearward from the back wheels of the vehicle. Trailer hitches are constructed such that the forward tongue portion of a trailer towed behind such vehicles is coupled to the vehicle at a point slightly rearward of the rear bumper of the vehicle. Even a slight right and left lateral shifting of the forward end of the towing vehicle results in concomitant left and right lateral shifting of the forward end of the trailer. This feature of a passenger vehicle trailer towing can be very dangerous, particularly if the trailer is improperly loaded such that the gross load of the trailer has a center of gravity disposed forward of the wheels of the trailer. The problem is evn more pronounced when the towed trailer has a large side elevational area upon which crosswind gusts and slip stream blasts may act.
Accordingly, a need exists for a trailer hitch connection between a vehicle and a trailer that will eliminate the sway tendencies of the vehicle and trailer combination as a result of slight lateral shifting of the forward end of the towing vehicle. Various solutions to the problem of trailer sway have been proposed, and anti-sway trailer hitches that include at least some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 2,201,660, 2,913,256, 3,254,905, 3,785,680, 3,787,077 and 3,825,282.
The most closely related improvement in anti-sway trailer hitch assemblies was disclosed in U.S. Pat. No. 4,582,337, by the present inventor. The ""337 patent teaches an anti-sway trailer hitch constructed in a manner whereby slight lateral deflections to the right and left by the front end of a towing vehicle will not be directly transmitted to the trailing vehicle in the form of left and right lateral swaying movements. The inventive anti-sway trailer hitch is relatively simple, including only three major components other than the usual forward-projecting trailer tongue assembly and may therefore be readily incorporated into the manufacture of new trailers and trailer hitches as well as retrofitted to existing trailers and trailer hitches. Specifically, the hitch construction includes an elongated hitch bar, first connecting means pivotally attaching one end of the bar to the rear towing portion of said vehicle, means pivotally anchoring an intermediate length portion of the bar to the forward portion of the trailing vehicle for angular displacement of the hitch bar about a first upstanding axis relative to the forward portion, a control member pivotally supported from the forward portion of the trailing vehicle for angular displacement about a second upstanding axis spaced rearward of the first axis, second connecting means pivotally and slidably connecting the other end of the bar to the control member at a point spaced forward of the second axis, control means connected between the rear portion and the control member, wherein the control means includes an elongated link, means pivotally connecting one end of the link to the rear portion for angular displacement about a third upstanding axis spaced to one lateral side of the first connecting means, and means pivotally connecting the other end of the link to the control member for angular displacement about a fourth upstanding axis spaced to the same lateral side of the second axis.
The inventive hitch assembly taught in the ""337 patent provides an anti-sway trailer hitch which may be utilized to couple a trailer to a towing vehicle in a manner such that slight lateral left and right movements of the forward end of the towing vehicle will not be transferred into lateral left and right movements, respectively, of the forward end of the towing vehicle. It also provides a hitch that may be readily retrofitted to existing trailer hitches and trailers; that provides an adjustment feature enabling adjustment of the anti-sway action of the hitch in accordance with the gross load represented by the associated trailer; and that provides an anti-sway trailer hitch made in the conventional forms of manufacture, is of simple construction and is easy to use so as to provide a device that will be economically feasible, long lasting and relatively trouble free in operation.
The hitch assembly of the present invention connects a rear wheel drive-towing vehicle and a towed vehicle. The forward end of the trailer is provided with a tongue or frame structure that extends forward and includes a trailer socket coupler. The hitch assembly includes a hitch beam extending transversely at the rear of the towing vehicle and rigidly affixed to the frame. The hitch beam has pivots points at each of its ends. The center of the hitch beam includes a towing vehicle hitch ball to which is connected an intermediate bar having a forward end and a rearward end, and includes a hitch bar having a hitch ball socket at the forward end for pivotal connection with the hitch ball. A hitch bar extension is detachably connected to the hitch bar.
A pair of compressible and extendable control rods are connected to opposite ends of the hitch beam by a detachable connection. The control rods have a forward end and a rear end and preferably comprise a first spring-biased control rod and a second spring-biased control rod. Each control rod includes a tubular sleeve having a forward end with a rod adjustably and threadbly affixed, and the rod can be adjusted in relation to tubular sleeve to accommodate different lengths of hitch bar and extension. The rear end of the tubular sleeve receives a movable rod with a coiled compression spring engaging an end flange on the tubular sleeve.
The rear end of the control rods are connected by a universal detachable connections to a control beam having ends and a central portion. The control beam between rod connections is preferably longer than the hitch beam between connections at the forward ends of the control rods.
A trailer coupler is pivotally connected to the central portion of the control beam. The coupler extends forward and rearward of the control beam, and the rearward end of the coupler is provided with a trailer hitch ball engaged by the trailer socket coupler. The pivotal connection includes a laterally extending arm at the upper end thereof, the arm being rigid with the control beam and pivotal in relation to the trailer coupler. The forward end of the trailer coupler has a pivotal connection that extends through the forward end of the trailer coupler and rearward portion of the hitch bar extension.
The pivotal movement between the trailer coupler and hitch bar extension is controlled by a roller rotatably journalled on a pin extending upwardly from the forward end of the arm and through a rotatable sleeve interposed between the upper surface of the arm and the lower end of the roller. The forward end of the arm is received within a downwardly opening slot in the rearward end portion of the hitch bar extension. The roller is located intermediate the pivot axis defined by the pivot bolt and the pivot connection forming the pivotal connection between the control beam and the trailer coupler. Accordingly, the pivotal movement of the hitch bar extension, the trailer coupler, and the control beam is controlled by the arm and the roller engaged in the slot.
When the towing vehicle turns, one end of the hitch beam exerts a pulling force on its correspondingly connected control rod, which through a rearward connection pulls on the same side of the control beam. The other end of the hitch beam exerts a pushing force against the corresponding end of the control beam through its corresponding control rod by compressing its spring. The combined pulling force on one side and pushing force on the other side on the control beam causes the control beam and arm to pivot about the central pivotal connection. When the articulated vehicles are moving in a relatively straight line, a very small pivotal and lateral movement of the hitch beam will cause large pivotal movement of the tow bar extension and trailer coupler. When the components are angled sharply from a straight line condition, a large movement of the hitch beam, hitch-ball, and control beam will produce a relatively small pivot movement of the tow bar extension and trailer coupler, proportionately small compared to the vehicle turning angle.